EP0568936B1 - Flüssigkeitströpfchen-Erzeuger - Google Patents

Flüssigkeitströpfchen-Erzeuger Download PDF

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Publication number
EP0568936B1
EP0568936B1 EP93107059A EP93107059A EP0568936B1 EP 0568936 B1 EP0568936 B1 EP 0568936B1 EP 93107059 A EP93107059 A EP 93107059A EP 93107059 A EP93107059 A EP 93107059A EP 0568936 B1 EP0568936 B1 EP 0568936B1
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European Patent Office
Prior art keywords
fluid
housing
piston
manifold
transducer
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EP93107059A
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English (en)
French (fr)
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EP0568936A1 (de
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John Lawrence Dressler
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B17/00—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups
    • B05B17/04—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods
    • B05B17/06—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods using ultrasonic or other kinds of vibrations
    • B05B17/0607—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods using ultrasonic or other kinds of vibrations generated by electrical means, e.g. piezoelectric transducers

Definitions

  • the present invention relates to a liquid droplet generator of the kind as defined in the preamble of claim 1 or claim 12. Furthermore, the invention concerns a method for generating droplets as defined in the preamble of claim 8.
  • the atomization of a jet or sheet of liquid is a process which, in most cases, requires energy to be added to the liquid.
  • the added energy is converted into an increase in surface energy in the liquid as the initial liquid mass is separated into droplets.
  • the surface area of the liquid likewise increases.
  • Energy may be supplied for purposes of atomization from either a decrease in kinetic energy of the liquid or from an external source.
  • UA-A-4 138 687 teaches a droplet generator and a method for generating droplets as defined in the preambles of claims 1 or 12 and claim 8, respectively.
  • the ink jet dispenser which is shown therein is an atomizer with less efficiency.
  • the electromechanically driven piston is mounted through a compliant mount to a nozzle plate.
  • the top and bottom ends of a transducer are free to move up and down, so that when a piezoelectric material extends, the piston moves as a result of the inertial reaction of the other end of the piezoelectric transducer.
  • the compliant mount is provided to prevent vibrations in the structure of the ink jet printer. Furthermore, the compliant mount also prevents the piston from placing a large compression on a manifold when a low frequency or steady voltage is applied to the transducer.
  • One prior art process for atomizing a fluid involves impinging a fast moving air stream onto a slower moving fluid, such as a fuel to be burned in a combustor of a turbine engine. With this process, the kinetic energy of the injected air serves to tear the liquid into filaments and then into drops. Thus, a portion of the kinetic energy of the injected air is converted into an increase in surface energy in the atomized fluid.
  • the prior art air injection process when used to atomize a fuel to be burned in a turbine engine, is only effective when the engine is operating, since a source of high velocity air is needed for atomization. Further, higher engine operating temperatures, which result in greater engine operating efficiency, are difficult to achieve since excess air is added into the engine for purposes of atomization. Additionally atomization by use of injected air results in an inconsistent distribution of fuel spray in both time and space. As a result, the combustor is required to be longer than otherwise necessary to ensure that all the fuel is burned before the air/fuel mixture exits the combustor. The inconsistent distribution of fuel spray also results in a non-uniform combustion of the air/fuel mixture causing an increase in NOx pollutants being emitted from the engine.
  • a further prior art atomization process involves the acoustic excitation of a circular liquid jet at an unstable wavelength.
  • Rayleigh explained in 1878 that a circular fluid jet is unstable for azimuthally symmetric perturbations whose axial wavelength is longer than the circumference of the jet.
  • This prior art process is based upon Rayleigh's theoretical work. The process involves placing small amplitude acoustic perturbations on a circular jet, wherein the perturbations have a wavelength longer than the circumference of the jet.
  • the applied perturbations grow, due to an input of energy from surface tension, and break the jet into a stream of drops at the excitation frequency. This process adds little or no energy to the fluid.
  • the surface area and surface energy of the fluid is lower after break-up than before.
  • the size of the resulting drops produced by this process have a diameter approximately twice the diameter of the original jet.
  • small nozzles or orifices must be used.
  • Small nozzles can be easily obstructed by particles carried by a fluid. Consequently, this process is disadvantageous for use where small droplets are desired. Further, this process will not induce atomization of a sheet of liquid.
  • an apparatus which is capable of adding energy to a liquid stream for purpose of atomization without employing high velocity air.
  • a high energy, acoustic droplet generator is provided for imparting energy into a stream of liquid in the form of velocity perturbations for purposes of atomizing the fluid into a stream of droplets. Because energy is added to the liquid stream, the surface area of the surface energy of the resulting stream of droplets is greater than that of the initial liquid stream.
  • a droplet generator for breaking a fluid jet into a stream of droplets.
  • the droplet generator comprises a housing having a first end, a second end, and an inner cavity.
  • the second end of the housing has at least one orifice therein.
  • An acoustic transducer is connected to the housing and has a first portion located within the cavity and spaced a given distance from the second end of the housing.
  • the first portion of the acoustic transducer and the second end of the housing define a manifold therebetween for receiving a fluid.
  • Fluid supply means are connected to either the housing or the acoustic transducer for supplying fluid under pressure to the inner cavity and into the manifold.
  • the fluid passes from the manifold via the orifice as a stream of fluid.
  • Drive means are provided for driving the transducer and causing the first portion of the transducer to impart acoustic energy to the fluid in the manifold, thereby creating velocity perturbations on the stream of fluid which are sufficient to atomize the fluid.
  • the acoustic transducer according to the invention comprises the features of claim 1 or claim 12.
  • the piezoelectric means may comprise at least two piezoelectric crystals.
  • the mount includes a centrally located stepped bore.
  • Each of the piezoelectric crystals includes a centrally located bore extending therethrough, while the piston includes a centrally located threaded bore which extends at least partially therethrough.
  • the connector means may comprise a bolt which extends through the bores in the mount and the piezoelectric crystals and threadedly engages with the threaded bore in the piston for connecting the mount, the piezoelectric crystals, and the piston to one another.
  • the bolt preferably includes a centrally located passage extending therethrough.
  • the piston includes at least one additional bore extending from an outer surface thereof to communicate with the centrally located passage extending through the bolt.
  • the fluid supply means communicates with the passage in the bolt for supplying fluid through the passage and the at least one additional bore in the piston to the cavity and into the manifold.
  • the drive means serves to drive the transducer at a natural frequency of the transducer. This causes large amplitude oscillations of the first portion of the transducer, thereby resulting in the first portion of the transducer imparting acoustic energy to the fluid in the manifold which results in large amplitude velocity perturbations on the stream of fluid.
  • the housing includes a hollow main portion having first and second ends.
  • the first end of the main portion defines the first end of the housing.
  • a nozzle plate is connected to the second end of the hollow main portion.
  • the nozzle plate defines the second end of the housing and has the at least one orifice formed therein.
  • the housing comprises a hollow main portion having first and second ends.
  • the first end of the main portion defines the first end of the housing.
  • An intermediate nozzle plate support is connected to the second end of the hollow main portion.
  • a nozzle plate is connected to the nozzle plate support and has the one orifice formed therein. The nozzle plate and the intermediate plate define the second end of the housing.
  • a method for generating droplets from a stream of liquid. The method comprises the steps indicated in claim 8.
  • the piezoelectric means may comprise at least two piezoelectric crystals.
  • the mount, the piezoelectric crystals, and the piston include bores as discussed above with regard to the first aspect of the present invention.
  • the step of connecting the mount, the piston and the piezoelectric means to one another is performed by passing a bolt through the bores in the mount and the piezoelectric crystals and threadedly engaging the bolt with the bore in the piston for connecting the piezoelectric crystals, the mount and the piston to one another.
  • the bolt includes a centrally located passage extending therethrough.
  • the piston includes an additional bore extending from an outer surface of the piston to communicate with the centrally located passage extending through the bolt.
  • the step of supplying fluid to the inner cavity and into the manifold is performed by passing fluid through the passage in the bolt and the additional bore in the piston to the cavity and into the manifold.
  • the step of driving the transducer is performed at a natural frequency thereof causing large amplitude oscillations of the first portion of the transducer, thereby resulting in the first portion imparting acoustic energy to the fluid in the manifold which results in large amplitude velocity perturbations on the stream of fluid.
  • a droplet generator constructed in accordance with the present invention is shown in Figures 1 and 2, and is generally designated by the reference numeral 10.
  • the droplet generator 10 includes a housing 20 having a substantially cylindrical main body portion 22 and an exit portion 24. Upper end 22a of the main body portion 22 defines a first end of the housing 20 and exit portion 24 defines a second end of the housing 20. Connected to the main body portion 22 of the housing 20 is an acoustic transducer 30.
  • the transducer 30 includes a piston 32 (also referred to herein as a first portion of the transducer) located within an inner cavity 26 of the housing and spaced a given distance (e.g., between 0,254 mm (0.010 in.) and 0,635 mm (0.025 in.)) from an entrance surface 24a of the exit portion 24 of the housing 20.
  • the piston 32 and the entrance surface 24a define a manifold 40 therebetween for receiving a fluid.
  • Drive means 50 is connected to the transducer 30 for driving the transducer 30 and causing the piston 32 to impart acoustic energy to the fluid in the manifold 40, thereby creating high amplitude velocity perturbations on the outgoing stream of fluid which are sufficient to atomize the fluid into a stream of droplets 60, as shown in Figure 1. Because energy is added to the stream of droplets 60, the surface area and the surface energy of the droplets 60 is greater than that of the initial liquid mass from which the droplets are formed.
  • a fluid supply 62 communicates with the acoustic transducer 30 through a fluid supply line 64 for providing pressurized fluid to the transducer 30.
  • the fluid supplied to the transducer 30 passes from the transducer 30 into the inner cavity 26 and into the manifold 40.
  • the fluid exits from the generator 10 via orifices or nozzles 70 formed within a nozzle plate 72, which comprises a first section of the exit portion 24 of the housing 20.
  • the orifices 70 are formed in the plate 72 as a linear array of spaced apart circular openings (see Figure 7),
  • the acoustic transducer 30 includes a mount 33 fixedly connected to the main body portion 22 of the housing 20 via bolts 33a. Positioned between the mount 33 and the piston 32 are two piezoelectric crystals 34 having an electrode 35 interposed therebetween. The electrode 35 extends through a slot 28 in the main body portion 22 for connecting with the drive means 50, as illustrated in Figure 1.
  • the drive means serves to drive the transducer 30 for causing the piston 32 to oscillate relative to the exit portion 24 of the housing 20 and impart acoustic energy to the fluid in the manifold 40 to atomize the fluid.
  • a bolt 38 (also referred to herein as connector means) is provided for connecting the piston 32, the mount 33, the piezoelectric crystals 34, and the electrode 35 to one another to form the transducer 30.
  • the bolt 38 passes through a centrally located stepped bore 33b in the mount 33, a centrally located bore 34a in each of the piezoelectric crystals 34 and a bore 35a located in the electrode 35.
  • the upper portion 38a of the bolt 38 seats in the stepped bore 33b in the mount 33, while the lower portion 38b threadedly engages with a centrally located threaded bore 32a in the piston 32.
  • the transducer 30 further includes sealing means comprising an O-ring 39 for sealing the piston 32 to the main body portion 22 of the housing 20 and thereby forming a sealed chamber 42 for receiving the fluid. At least a portion of the piston 32 is positioned within the chamber 42 and a section of the chamber 42 is defined by the manifold 40.
  • the bolt 38 includes a centrally located passage 38c extending therethrough, as shown in dotted line in Figure 2.
  • the piston 32 includes an additional bore 32b extending from an outer surface 32c of the piston 32 for communicating with the centrally located passage 38c extending through the bolt 38.
  • the fluid supply line 64 is connected to the mount 33 via connector 65 and communicates with the passage 38c in the bolt 38 for supplying fluid through the passage 38c and the additional bore 32b in the piston 32 to the sealed chamber 42 and into the manifold 40.
  • the fluid supply means 62 preferably supplies fluid through line 64 at a pressure between 6,896 - 41,376 N/cm 2 (10-60 psi).
  • a nozzle support plate 74 is interposed between the nozzle plate 72 and the main body portion 22 of the housing 20.
  • the support plate 74 comprises a second section of the exit portion 24 of the housing 20 and its upper surface defines the entrance surface 24a of the exit portion 24 of the housing 20.
  • the nozzle support plate 74 includes a centrally located opening 74a through which the fluid passes before it exits through the orifices 70 in the nozzle plate 72.
  • Bolts 76 pass through corresponding openings in the plates 72 and 74 and threadedly engage with corresponding openings 22b found in the main body portion 22 of the housing 20 to secure the plates 72 and 74 to the main body portion 22.
  • Adhesive (not shown), such as an epoxy, may be interposed between the nozzle support plate 74 and the nozzle plate 72 for further securing and sealing the nozzle plate 72 to the nozzle support plate 74.
  • the nozzle support plate 74 acts to increase the rigidity of the nozzle plate 72.
  • a more rigid nozzle plate 72 allows for a more efficient conversion of the oscillatory effects of the piston 32 to fully periodically compress the fluid thereby forming pressure perturbations in the fluid within the manifold 40.
  • the nozzle plate 72 may alternatively be attached directly to the main body portion 22 of the housing 20 via bolts 76.
  • the drive means 50 preferably comprises the driving circuit 52 shown in Figure 8, and disclosed in US-A-3 868 698 (entitled “Stimulation Control Apparatus for an Ink Jet Recorder,” issued February 25, 1975), the disclosure of which is incorporated herein by reference.
  • the driving circuit includes a differential amplifier 53, a power amplifier 54, a load resistor 55, and negative and positive feedback loops to the negative and positive input terminals 53a and 53b of the differential amplifier 53.
  • the negative feedback loop extends from output terminal 53c of differential amplifier 53 back around to the negative input terminal 53a.
  • the negative feedback loop therefore includes load resistor 55 and branches out into two branches at the output side thereof.
  • One of these two negative branches includes only a resistor 56, whereas the other branch comprises a peak detector 57a, a differential amplifier 57b and a voltage dependent resistance 57c.
  • the positive feedback loop extends from output terminal 53c back through an R-C network to the positive input terminal 53b.
  • the positive feedback loop comprises resistors 58a and 58b and capacitors 59a and 59b connected in a wien bridge arrangement.
  • the circuit 52 serves to drive the transducer 30 at a natural frequency thereof and to track that frequency as it changes normally due to heating or other causes during operation of the droplet generator 10.
  • the transducer 30 normally has more than one natural frequency. Consequently, it is usually possible to drive the piezoelectric crystals 34 at more than one frequency. Additionally, several frequencies may be placed on the crystals 34 at the same time.
  • the amplitude of motion of the bottom surface 32d of the piston 32 is much greater than the amplitude of motion of the crystals 34 combined. Consequently, the oscillating bottom surface 32d of the piston 32 imparts sufficient acoustic energy to the fluid in the manifold 40 to create large amplitude velocity perturbations on the fluid which result in atomization of the fluid into a stream of droplets.
  • a nozzle plate 80 constructed in accordance with a second embodiment of the present invention.
  • the nozzle plate 80 is formed having a nozzle 82 through which fluid in the manifold 40 exits from the droplet generator 10.
  • the plate 80 may be formed according to the process disclosed in US-A-4 528 070, the disclosure of which is incorporated herein by reference.
  • the plate 80 comprises first and second layers of nickel 84 and 86, respectively, and an intermediate layer of beryllium-copper 88 interposed therebetween, see Figures 11A and 11B.
  • the first layer 84 is formed with an entrance slot 84a through which the fluid first passes as it exits from the manifold 40.
  • the second layer 86 is formed with an exit slot 86a through which the fluid exits from the generator 10 after passing through the entrance slot 84a.
  • the entrance slot 84a is rotated from the exit slot 86a at an angle ⁇ , which is approximately 4°.
  • the entrance slot 84a has a length of approximately 5,588 mm (0,220 in.) and a width of approximately 0,1524 mm (0,006 in.), while the exit slot 86a has a length of approximately 5,334 mm (0,210 in.) and a width of approximately 0,0381 mm (0,0015 in.).
  • the thickness of the plate 80 including the first, second and intermediate layers 84, 86 and 88, respectively, is approximately 0,254 mm (0,010 in.).
  • a stream of droplets formed by a droplet generator 10 according to the present invention employing the nozzle plate 80 is shown in the photograph of figure 12.
  • the droplet generator 10 included a nozzle support plate 74 having a thickness of approximately 6,35 mm (0,25 in.).
  • the fluid supplied to the generator 10 comprised a formulation of water to glycerol in a weight ratio of 4:6.
  • the fluid was supplied to the generator 10 at a pressure of approximately 21,17 N/cm 2 (33.6 psi).
  • the drop generator transducer 30 was driven at a frequency of approximately 9.78 kHz, which was approximately equal to a natural frequency of the transducer 30.
  • the fluid as it exits from the generator 10, first breaks into a plurality of horizontal filaments and then into a plurality of droplets.
  • the nozzle plate 90 includes a nozzle 92 through which fluid in the manifold 40 exits from the droplet generator 10.
  • the nozzle plate 90 may be formed according to the process disclosed in US-A 4,528,070.
  • the nozzle plate 90 includes first and second layers of nickel 94 and 96, respectively, and an intermediate layer of beryllium-copper 98 interposed therebetween, see Figure 14.
  • the first layer 94 is formed with an entrance slot 94a through which the fluid first passes as it exits from the manifold 40.
  • the second layer 96 is formed with an exit slot 97 through which the fluid exits from the generator 10 after passing through the entrance slot 94a.
  • the entrance slot 94a is rotated from the exit slot 97 at an angle ⁇ (shown exaggerated in Figure 13), which is approximately 3.4°.
  • the entrance slot 94a has a length of approximately 5,334 mm (0,210 in.) and a width of approximately 0,1524 mm (0,006 in.).
  • the exit slot 97 is formed with a plurality of perturbations 97a, each having a length L 1 equal to approximately 1,016 mm (0,040 in.).
  • the exit slot 97 has a length of approximately 6,096 mm (0,240 in.) and has a first width W 1 equal to 0,0762 mm (0,003 in.) and a second width W 2 equal to 0,0381 mm (0,0015 in.).
  • the thickness of the plate 90 including the first, second and intermediate layers 94, 96 and 98, respectively, is approximately 0,254 mm (0,010 in.).
  • a stream of droplets formed by a droplet generator 10 according to the present invention employing the nozzle plate 90 is shown in the photograph of Figure 15.
  • the droplet generator 10 included a nozzle support plate 74 having a thickness of approximately 6,35 mm (0.25 in.).
  • the fluid supplied to the generator 10 comprised a formulation of water to glycerol in a weight ratio of 4:6.
  • the fluid was supplied to the generator 10 at a pressure of approximately 21,17 N/cm 2 (33.6 psi).
  • the drop generator transducer 30 was driven at a frequency of approximately 5.55 kHz, which was approximately equal to a natural frequency of the transducer 30.
  • As shown in the photograph as the fluid sheet exits from the generator 10, it breaks into horizontal filaments and then into a plurality of droplets.
  • the nozzle plate 100 includes a nozzle 102 through which fluid in the manifold 40 exits from the droplet generator 10.
  • the plate 100 may be formed according to the process disclosed in US-A-4 528 070.
  • the plate 100 includes first and second layers of nickel 104 and 106, respectively, and an intermediate layer of beryllium-copper 108 interposed therebetween, see Figure 17.
  • the first layer 104 is formed with an entrance slot 104a through which the fluid first passes as it exits from the manifold 40.
  • the second layer 106 is formed with an exit slot 107 through which the fluid exits from.
  • the entrance slot 104a has a length of approximately 5,334 mm (0.210 in.) and a width of approximately 0,0381 mm (0.0015 in.).
  • the exit slot 107 includes a plurality of perturbations 107a, each having a length L a equal to 0,254 mm (0.010 in.).
  • the exit slot 107 has a length of approximately 5,334 mm (0.210 in.) and a first width W a approximately equal to 0,0508 mm (0.002 in.) and a second width W b approximately equal to 0,0381 mm (0.0015 in.).
  • the entrance slot 104a is offset from the exit slot 107 by a distance D which is approximately equal to 0,0254 mm (0.001 in.).
  • the thickness of the plate 100 including the first, second and intermediate layers 104, 106 and 108, respectively, is approximately 0,254 mm (0.010 in.).
  • a stream of droplets formed by a droplet generator 10 according to the present invention employing the nozzle plate 100 is shown in the photograph of Figure 18.
  • the droplet generator 10 included a nozzle support plate 74 having a thickness of approximately 6,35 mm (0.25 in.).
  • the fluid supplied to the generator 10 comprised a formulation of water to glycerol in a weight ratio of 4:6.
  • the fluid was supplied to the generator 10 at a pressure of approximately 21,17 N/cm 2 (33.6 psi).
  • the drop generator transducer 30 was driven at a frequency of approximately 9.64 kHz, which is approximately equal to a natural frequency of the transducer 30.
  • the fluid breaks into a plurality of droplets as it exits from the nozzle 102 at an angle from vertical.
  • a method and apparatus are provided for imparting energy into a stream of liquid in the form of velocity perturbations for purposes of atomizing the liquid into a stream of droplets. Because energy is imparted into the stream of liquid, the liquid atomizes into a stream of droplets having a surface area and surface energy greater than that of the initial stream.
  • droplet generator 10 of the present application may be employed in applications such as agricultural spraying, spray drying and fuel injection.
  • the transducer 30 may be driven with a high voltage so as to create large amplitude oscillations of the piston 32. It is additionally contemplated that several piezoelectric crystal pairs can be employed, and each pair may be driven at a different frequency.

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  • Special Spraying Apparatus (AREA)
  • Fuel-Injection Apparatus (AREA)

Claims (12)

  1. Tröpfchenerzeuger (10), der folgendes umfaßt:
    ein Gehäuse (20) mit einem ersten Ende (22a), einem zweiten Ende (24) und einer inneren Aushöhlung (26), wobei das zweite Ende wenigstens eine Auslaßöffnung (70) aufweist;
    einen akustischen Wandler (30) mit einem ersten Teil, der innerhalb der Aushöhlung in einem vorgegebenen Abstand zum zweiten Ende (24) des Gehäuses angeordnet ist, wobei zwischen dem ersten Teil des akustischen Wandlers und dem zweiten Ende des Gehäuses ein Verteiler (40) zur Aufnahme eines Fluids definiert wird;
    eine Befestigung (33) für den Wandler, die fest mit dem ersten Ende des Gehäuses verbunden ist;
    einen Kolben (32), der innerhalb der Aushöhlung im wesentlichen abgedichtet ist, um den Verteiler im wesentlichen abzutrennen und den ersten Teil des Wandlers zu bilden;
    ein Mittel zur Fluidzuführung (62), das mit dem Gehäuse oder mit dem akustischen Wandler zur Zuführung von Fluid unter Druck in den Verteiler verbunden ist, wobei das Fluid aus dem Verteiler durch die Öffnung (70) als Fluidstrom (60) strömt;
    wobei der Wandler ein piezoelektrisches Mittel (34) aufweist und mit dem Kolben verbunden ist, um den Kolben relativ zu dem zweiten Ende (24) des Gehäuses in Schwingung zu versetzen und akustische Energie auf das Fluid in dem Verteiler zu übertragen und dadurch Geschwindigkeitsschwankungen des Fluidstroms hervorzurufen, die ausreichen, um das Fluid zu zerstäuben,
       dadurch gekennzeichnet, daß der Wandler mit dem piezoelektrischen Mittel (34) zwischen dem Gehäuse (20) und dem Kolben (32) angeordnet ist, und daß ein Verbindungsmittel (38) vorgesehen ist, um die Befestigung, das Gehäuse, den Kolben und das piezoelektrische Mittel starr miteinander zu verbinden, wodurch das Fluid vollständig periodisch in dem Verteiler durch den Kolben gegen das feste zweite Ende des Gehäuses komprimiert wird, wodurch Druckschwankungen hervorgerufen werden, um die Zerstäubung des Fluids zu steigern.
  2. Tröpfchenerzeuger nach Anspruch 1, dadurch gekennzeichnet, daß das piezoelektrische Mittel wenigstens zwei piezoelektrische Kristalle (34) umfaßt.
  3. Tröpfchenerzeuger nach Anspruch 1, dadurch gekennzeichnet, daß die Befestigung eine mittig angeordnete abgestufte Bohrung (33b) aufweist;
    daß jedes piezoelektrische Kristall eine mittig angeordnete, sich durch es hindurch erstreckende Bohrung (34a) aufweist;
    daß der Kolben eine mittig angeordnete, sich wenigstens teilweise durch ihn hindurch erstreckende Gewindebohrung (32a) aufweist; und
    daß das Verbindungsmittel (38) eine Schraube umfaßt, die sich durch die Bohrungen in der Befestigung und in den piezoelektrischen Kristallen erstreckt und in das Gewinde der Bohrung des Kolbens eingeschraubt ist, um die Befestigung, die piezoelektrischen Kristalle und den Kolben miteinander zu verbinden.
  4. Tröpfchenerzeuger nach Anspruch 1, dadurch gekennzeichnet, daß die Schraube einen sich durch sie hindurch erstreckenden, mittig angeordneten Durchlaß (38c) aufweist;
    daß der Kolben wenigstens eine zusätzliche Bohrung (32b) aufweist, die von dessen äußerer Oberfläche ausgeht und mit dem sich durch die Schraube erstreckenden, mittig angeordneten Durchlaß in Verbindung steht; und
    daß das Mittel zur Fluidzuführung mit dem Durchlaß in der Schraube zur Zuführung des Fluids über den Durchlaß und über die wenigstens eine zusätzliche Bohrung in dem Kolben zu dem Verteiler in Verbindung steht.
  5. Tröpfchenerzeuger nach Anspruch 1, dadurch gekennzeichnet, daß das piezoelektrische Mittel (34) den Wandler mit einer diesem eigenen Resonanzfrequenz antreibt, wodurch große Amplitudenschwingungen des Kolbens hervorgerufen werden und der Kolben (32) dadurch akustische Energie auf das Fluid überträgt und das Fluid in dem Verteiler periodisch komprimiert, wodurch große Schwankungen in der Amplitude der Geschwindigkeit und des Drucks auf und in dem Fluidstrom erreicht werden.
  6. Tröpfchenerzeuger nach Anspruch 1, dadurch gekennzeichnet, daß das Gehäuse (20) folgendes umfaßt:
    einen hohlen Hauptabschnitt mit einem ersten und einem zweiten Ende, wobei das erste Ende des Hauptabschnitts das erste Ende des Gehäuses bildet; und
    eine Düsenplatte (72, 74), die mit dem zweiten Ende des hohlen Hauptabschnitts fest verbundenen ist, wobei die Platte das feste zweite Ende des Gehäuses bildet und die darin vorgesehene Öffnung hat.
  7. Tröpfchenerzeuger nach Anspruch 1, dadurch gekennzeichnet, daß das Gehäuse (20) folgendes aufweist:
    einen hohlen Hauptabschitt mit einem ersten und einem zweiten Ende, wobei das erste und das zweite Ende des Hauptabschnitts das erste bzw. das zweite Ende des Gehäuses bilden;
    eine Düsenzwischenplattenabstützung (72), die mit dem zweiten Ende des hohlen Hauptabschnitts verbunden ist; und
    eine Düsenplatte (74), die mit der Düsenplattenabstützung fest verbunden ist, wobei die Öffnung in der Düsenplatte ausgebildet ist und die Düsenplatte und die Zwischenplatte das feste zweite Ende des Gehäuses bilden.
  8. Verfahren zur Erzeugung von Tröpfchen, das folgende Schritte aufweist:
    Bereitstellen eines Gehäuses (20) mit einem ersten Ende (22a), einem zweiten Ende (24) und einer inneren Aushöhlung, wobei das zweite Ende wenigstens eine Auslaßöffnung (70) aufweist;
    Bereitstellen eines akustischen Wandlers (30); einer Befestigung (33) für den Wandler, die fest mit dem ersten Ende des Gehäuses verbunden ist;
    Anordnen eines ersten Teils des Wandlers innerhalb der Aushöhlung und Definieren eines Kolbens (32), der in einem vorgegebenen Abstand von dem festen zweiten Ende (24) des Gehäuses angeordnet ist, wobei zwischen dem Kolben und dem festen zweiten Ende des Gehäuses ein Verteiler (40) zur Aufnahme eines Fluids definiert wird;
    Zuführen von Fluid unter Druck in den Verteiler;
    Abdichten (39) des Kolbens innerhalb der Aushöhlung, um den Verteiler im wesentlichen zu abzutrennen;
    Führen des Fluids von dem Verteiler durch die Öffnung (70) als Fluidstrom (60); und Antreiben des akustischen Wandlers (30), der ein piezoelektrisches Mittel (34) aufweist, und Hervorrufen einer Übertragung akustischer Energie auf das Fluid in dem Verteiler durch den Kolben (32), so daß das Fluid periodisch unter Bildung von Druckschwankungen gegen das feste zweite Ende (24) komprimiert wird und dadurch Geschwindigkeits- und
    Druckschwankungen auf und in dem Fluidstrom erzeugt werden, die ausreichen, um das Fluid zu zerstäuben, gekennzeichnet durch starres Befestigen des akustischen Wandlers (30) an dem Gehäuse (20) mit dem ersten Ende durch Anordnen des Wandlers mit dem piezoelektrischen Mittel (34) zwischen dem Gehäuse (20) und dem Kolben (32) und durch Vorsehen eines Verbindungsmittels (38), um die Befestigung, das Gehäuse, den Kolben und das piezoelektrische Mittel starr miteinander zu verbinden.
  9. Verfahren zum Erzeugen von Tröpfchen nach Anspruch 8, dadurch gekennzeichnet, daß das Antreiben des akustischen Wandlers (30) durch Aktivierung eines piezoelektrischen Mittels (34) vorgenommen wird.
  10. Verfahren zur Erzeugung von Tröpfchen nach Anspruch 8, dadurch gekennzeichnet, daß das Zuführen von Fluid in den Verteiler das Führen des Fluids durch den Wandler (30) und den Kolben (32) und anschließend in den Verteiler beinhaltet.
  11. Verfahren zur Erzeugung von Tröpfchen nach Anspruch 8, dadurch gekennzeichnet, daß das Antreiben des Wandlers (30) bei einer diesem eigenen Resonanzfrequenz erfolgt, wodurch große Amplitudenschwingungen des Kolbens (32) des Wandlers hervorgerufen werden, so daß eine Übertragung akustischer Energie auf das Fluid in dem Verteiler (40) durch den ersten Teil und damit große Schwankungen in der Amplitude der Geschwindigkeit des Fluidstroms hervorgerufen werden.
  12. Tröpfchenerzeuger, der folgendes umfaßt:
    ein Gehäuse (20) mit einem ersten Ende (22a), einem zweiten Ende (24) und einer inneren Aushöhlung, wobei das zweite Ende wenigstens eine Auslaßöffnung (70) aufweist;
    einen im wesentlichen abgedichteten Kolben (32) innerhalb der Aushöhlung;
    einen akustischen Wandler (30), der mit dem Gehäuse oder dem Kolben verbunden ist;
    wobei der Kolben (32) in einem vorgegebenen Abstand von dem zweiten Ende (24) des Gehäuses angeordnet ist und dazwischen einen Verteiler (40) zur Aufnahme eines Fluids definiert;
    eine Dichtung (39) zwischen dem Kolben und dem Gehäuse innerhalb der Ausnehmung, um den Verteiler im wesentlichen von dem ersten Ende (22a) des Gehäuses abzudichten und abzutrennen;
    eine Befestigung (33), die fest mit dem ersten Ende des Gehäuses verbunden ist; und
    ein Mittel zur Fluidzuführung (62), das mit dem Gehäuse oder dem Kolben zur Zuführung von Fluid unter Druck in den Verteiler verbunden ist, wobei das Fluid aus dem Verteiler durch die Öffnung (70) als Fluidstrom (60) strömt;
    dadurch gekennzeichnet, daß der Wandler (30) zwischen dem Gehäuse und dem Kolben angeordnet ist, um den Kolben zu Schwingungen relativ zu dem zweiten Ende (24) des Gehäuses anzuregen und akustische Energie auf das Fluid in dem Verteiler zu übertragen, wodurch Geschwindigkeitsschwankungen des Fluidstroms erzeugt werden, die ausreichen, um das Fluid zu zerstäuben, und daß ein Verbindungsmittel (38) vorgesehen ist, um die Befestigung, das Gehäuse, den Kolben und den Wandler starr miteinander zu verbinden, wodurch das Fluid vollständig periodisch in dem Verteiler (40) durch den Kolben gegen das feste zweite Ende (24) des Gehäuses komprimiert wird und somit Druckschwankungen hervorgerufen werden, um die Zerstäubung des Fluids zu steigern.
EP93107059A 1992-05-08 1993-04-30 Flüssigkeitströpfchen-Erzeuger Expired - Lifetime EP0568936B1 (de)

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US880890 1992-05-08
US07/880,890 US5248087A (en) 1992-05-08 1992-05-08 Liquid droplet generator

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US5248087A (en) 1993-09-28
DE69321025T2 (de) 1999-05-12
EP0568936A1 (de) 1993-11-10
DE69321025D1 (de) 1998-10-22
JPH0642426A (ja) 1994-02-15
JP3345459B2 (ja) 2002-11-18

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